UPDATE: NASCAR responds.

The driver has been under scrutiny since November, when an investigation was opened in Dover, Delaware over allegations of domestic assault. Busch's former girlfriend, Patricia Driscoll, alleges that the NASCAR star choked and beat her inside his RV last fall at Dover International Speedway.

But today, the Delaware attorney general's office declared there was not enough evidence to bring criminal charges against Busch.

"After a thorough consideration of all of the available information about the case, it is determined that hte admissible evidence and available witnesses would likely be insufficient to meet the burden of establishing beyond a reasonable doubt that Mr. Busch committed a crime during the September 26th incident," said the attorney general's office in a prepared statement.

The very public nature of Driscoll's allegations against Busch took a decidedly bizarre turn in January, when Busch asserted, under oath, that his ex-girlfriend Driscoll was a trained assassin who once returned to their home from a covert mission wearing an evening gown spattered in blood.

UPDATE: NASCAR released a statement regarding Busch's status within the organization, copied in full here.

NASCAR is aware of the Delaware Department of Justice announcement today regarding driver Kurt Busch. As we disclosed Monday, he has accepted the terms and conditions of a reinstatement program and is actively participating in the program. Kurt Busch's eligibility for reinstatement will continue to be governed by that program and the NASCAR Rule Book, though the elimination of the possibility of criminal charges certainly removes a significant impediment to his reinstatement.